rust: pci: add resource_flags accessor

Add a `Device::resource_flags()` method to the PCI Rust abstraction,
wrapping the C-side static inline `pci_resource_flags()`.

The flags returned correspond to the `IORESOURCE` bitmask carried by a
PCI BAR's `struct resource`.

The immediate motivation is BAR layout discovery on NVIDIA GPUs: a
64-bit BAR consumes two consecutive Linux PCI resource slots (the lower
32 bits at index N and the upper 32 bits at index N+1, with the latter
having no flags or size of its own).

Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Link: https://patch.msgid.link/20260908-pci-resource-flags-v1-1-269f29f81de6@nvidia.com
Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/rust/kernel/io/resource.rs b/rust/kernel/io/resource.rs
index 17b0c174cfc5..0d3b34f83334 100644
--- a/rust/kernel/io/resource.rs
+++ b/rust/kernel/io/resource.rs
@@ -226,10 +226,18 @@ impl Flags {
     /// Resource represents a memory region that must be ioremaped using `ioremap_np`.
     pub const IORESOURCE_MEM_NONPOSTED: Flags = Flags::new(bindings::IORESOURCE_MEM_NONPOSTED);
 
+    /// Memory region uses a 64-bit address (consumes two consecutive PCI resource slots).
+    pub const IORESOURCE_MEM_64: Flags = Flags::new(bindings::IORESOURCE_MEM_64);
+
     // Always inline to optimize out error path of `build_assert`.
     #[inline(always)]
     const fn new(value: u32) -> Self {
         build_assert!(value as u64 <= c_ulong::MAX as u64);
         Flags(value as c_ulong)
     }
+
+    /// Wrap a raw `c_ulong` value returned by a C API into [`Flags`].
+    pub(crate) const fn from_raw(value: c_ulong) -> Self {
+        Flags(value)
+    }
 }